128763-87-1Relevant articles and documents
Basket-shaped hosts with semi-flexible handles
Smeets, J. W. H.,Visser, H. C.,Kaats-Richters, V. E. M.,Nolte, R. J. M.
, p. 147 - 153 (2007/10/02)
Basket-shaped hosts were synthesized starting from the concave building block 4: .To this end, oligo(oxyethylene)bridges, containing different aromatic rings, were attached to the 3,6- and 3',6'-positions of the xylylene rings of 4.These bridges include 5,6-benzo-1,4,7,10-tetraoxadec-5-ene, 5,6,7-benzo-1,4,8,11-tetraoxaundeca-5,6-diene, 5,6-(2,3-naphtho)-1,4,7,10-tetraoxa-dec-5-ene, 8,9-benzo-1,4,7,10,13,16-hexaoxahexadec-8-ene and 8,9-(2,3-naphtho)-1,4,7,10,13,16-hexaoxahexadec-8-ene chains.Alkali-metal ions and protonated aliphatic or aromatic diamines are bound in these baskets in a 1:1 host/guest ratio.For the metal ions, a clamshell-like or a sandwich-like complex is proposed.Aliphatic diammonium guests are bound in such a way that the methylene chains are wedged in between the o-xylylene units of the host, as concluded from the upfield shifts observed in the 1H NMR spectra of the guest CH2 protons.Free energies of binding of the new hosts with nineteen guests were measured using the picrate extraction technique.The highest -ΔG0 values were obtained for the complexes with the diammonium salts (-ΔG0 values up to 13.4 kcal/mol).
